Containers and screw caps of this kind are already known and described for example in published German Patent Application No. 1,043,847 dated Sept. 22, 1955. The advantage of this arrangement of the seal as an approximately circular seal section or as a seal fin which comes into engagement with the inner wall of the container, is primarily in that tolerances of the container neck can be compensated especially well by the deformable seal section.
However in practice these screw stoppers have not become established because of various drawbacks in design. One great disadvantage of these known screw stoppers is that the seal section comes into engagement with the container neck only after the screwing operation has commenced. This often leads to the seal section tilting slightly under the rotatory movement whilst being screwed into position, when it is pressed slowly into the container neck. The seal section is then irregularly bent back or even, in the case of major tilting, is so damaged that a satisfactory seal can no longer be achieved.
Especially in the bottling of liquids under pressure, such for example as beverages containing carbon dioxide, a further serious disadvantage of the known containers and screw stoppers is that frequently the seal sections are still in engagement with the container neck when the screw threads are already almost completely disengaged. This leads to the possibility of the screw stopper bursting explosively away from the container, whereby there is considerable danger of injury.